Motion system

ABSTRACT

A MOTION SYSTEM FOR AN AIRCRAFT SIMULATOR, OR THE LIKE OF THE TYPE WHEREIN INDEPENDENT ACTUATORS ARE PROVIDED FOR MOVING THE MOTION PLATFORM IN EACH SINGLE AXIS OF FREEDOM. THE PRESENT INVENTION PROVIDES SUCH A SYSTEM WITH GREATLY IMPROVED STRUCTURAL RIGIDITY AND EXACT DUPLICATION OF MOTION TRANSMITTED THROUGH A LINKAGE AT A NUMBER OF POINTS. IN THE DISCLOSED EMBODIMENT, VERTICAL TRANSLATION IS IMPARTED BY ROTATING FOUR BELL CRANK MEMBERS LINKED TO FOUR RESPECTIVE CORNERS OF A TRUSS, THE BELL CRANKS BEING CONNECTED IN A STRUCTURALLY CLOSED-LOOP MANNET TO ELIMINATE BACKLASH OR LOST MOTION IN THE LINKAGE.

Nov. 15, 1971 E. G. PANCOE MOTION SYSTEM Filed way 19, 1969 5Sheets-Shet l Nov. 16, 1971 E. G. PANCOE 3,619,911

MOTION SYSTEM Filed May 19, 1969 5 Sheets-Sheet :3

i f wy ak TM 3 Nov. 16, 1971 G, PANCOE 3,619,911

MOTION SYSTEM Filed Ray 19, 1969 5 Sheets-Sheet 5 Cm m E s. PANCOEMOTION SYSTEM Nov. 16, 1971 5 Sheets-Sheet 4 Filed Ray 19, 1969 NOV. 16,1971 PANCQE I 3,619,911

MOTION SYSTEM Filed lay 19, 1969 I 5 Sheets-Sheet 5 United States PatentOffice Iifilfifill Patented Nov. 16, 1971 3,619,911 MOTION SYSTEM EdwardG. Pancoe, Chenango Forks, N.Y., assignor to Singer-General Precision,Inc., Binghamton, N.Y. Filed May 19, 1969, Ser. No. 825,527 Int. Cl.G09b 9/08 US. Cl. 35-12 P 4 Claims ABSTRACT OF THE DISCLOSURE A motionsystem for an aircraft simulator, or the like, of the type whereinindependent actuators are provided for moving the motion platform ineach single axis of freedom. The present invention provides such asystem with greatly improved structural rigidity and exact duplicationof motion transmitted through a linkage at a number of points. In thedisclosed embodiment, vertical translation is imparted by rotating fourbell crank members linked to four respective corners of a truss, thebell cranks being connected in a structurally closed-loop man ner toeliminate backlash or lost motion in the linkage.

The present invention relates to motion simulators of the type commonlyutilized to provide controlled movement within specified limits to arigid platform which may carry the student station of a vehiclesimulator, or the like.

Vehicle simulator training apparatus in current use normally includes asystem for providing to the student station controlled velocities andaccelerations representative of the type likely to be encountered inoperation of the actual vehicle. The training value derived from thesimulator is thereby greatly enhanced by duplicating to some extent thesensory stimuli experienced in an actual vehicle of the type simulated.Motion is commonly provided to the student station by controlledactuation of rigid elements, such as linear actuators and the like. Suchsystems may be generally classified as being either of the synergistictype, wherein the movement of all actuators is required to producemovement of the student station in any one axis of freedom, or of thecascaded or independent type, wherein only one actuator need be moved toprovide motion in any single axis of freedom. These two types of motionsystems each have certain advantages and disadvantages, the selection ofone type or the other depending upon the desired performance andphysical design limitations placed on the system.

The present invention is concerned with motion systems of theindependent type having a plurality of motion actuators, each providingmovement of the student station in or about a distinct axis of freedom.Movement of the several actuators may be superimposed (i.e., effectedsimultaneously) to produce more complex motions in more than one degreeof freedom at any given time. The principal object of the invention isto provide a motion simulator of the independent type incorporating theusual advantages of such type of motion system while overcoming certaindisadvantages and providing advantages normally associated withsynergistic motion simulators. Extension and retraction movements of theactuators are transmitted to the student station, commonly supported ona rigid motion platform, through appropriate mechanical linkages in somecases, and through direct connection between the actuator and platformin others. It is desirable, of course, that the design of the linkagesbe such that minimal backlash or lost motion occurs during operation ofthe motion system. Also, the linkage should be as stable as possible;that is, the linkage must be restrained against movement in any otherthan the desired direction, either translational or rotational. Somelinkages further require means for insuring exact duplication of motiontransmission from side to side, or front to rear, of a truss, platform,or other such element supported at several points.

The present invention is directed toward providing a motion simulatorhaving an improved linkage with the desirable features enumerated above.In the disclosed embodiment, vertical translation is imparted to themotion platform through an arrangement of four bell cranks linked to thefour corners of a truss. This would normally introduce an unduly largeamount of backlash into the system and an accompanying disparity in theamount of motion transmitted to each corner of the truss. However,through the use of a unique, closed-loop structure, rotation of eachbell crank is identically duplicated by each of the others and a systemis provided with great fidelity of motion transmission as well assuperior stability with reasonable simplicity and economy, which is theprincipal object of the invention.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the features of construction,combinations of elements, and arrangement of parts, which will beexemplified in the construction hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the inventionreference should be had to the following detailed description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a side elevational view showing an exemplary form of theinvention with the apparatus in a rest or settled position;

FIG. 2 is a side elevation, as in FIG. 1, showing the apparatus in anerected or operational position, with a number of possible positions ofthe motion platform shown in dot dash lines;

FIG. 3 is a front elevation of the apparatus of the invention shown inan elevated position; and

FIGS. 4 and 5 are exploded perspective views of selected elements of theapparatus shown in FIGS. 1-3.

Prior art motion systems of the synergistic type are typified by themotion simulator shown in US. Pat. No. 3,295,224, and those of theindependent or cascaded type by U.S. Pats. Nos. 2,930,144 and 3,281,962,among others. Motion simulators of both types are commonly provided asan integral portion of many aircraft flight simulators, and similartraining apparatus, and operate with the motion actuators under thecontrol of appropriate analog or digital computer means. The presentinvention is likewise intended to be operated with linear actuatorswhich may be identical in construction and operation with thosedisclosed in prior publications, such as the patents mentioned above.Therefore, in the interest of clarity and brevity the present disclosurewill be limited to the mechanical configuration with which the inventionis primarily concerned, it being understood that appropriateservomechanisms, follow-up devices, computer hardware and software, andother such operational elements may be provided in accordance with priorart teachings.

A typical flight simulator cockpit of the type intended to provide thestudent station of the motion simulator is shown in FIG. 1 and indicatedby the reference numeral 10. Cockpit 10 is fixedly secured to rigidplatform 12 through which motions are transmitted to the studentstation. Platform 12 is supported at three points by means of suitablejoints, such as ball and socket or two axis gimbal joints, connectingthe platform to other rigid elements. The three points of support ofplatform 12 are best seen in FIG. 4, where they are indicated by thereference numerals 14, 16 and 18. Point 14 lies on the longitudinal axisof the platform, indicated by the line XX, point 16 l es on a transverseaxis, indicated by the line Y-Y, and point 18 lies at the intersectionof the two axes. The common designations roll and pitch will be usedhereinafter to refer to movements of platform 12 about the X and Y axes,respectively, and to describe elements used to produce such motions.

The platform is supported at points 14 and 18 by A- frame structures,indicated generally by the reference numerals 20 and 22, and at point 16by the movable end portion of the piston rod of hydraulic cylinder 24,comprising a portion of the linear actuator system by which roll motionof platform 12 is implemented. A-frame 20 extends from its connection atpoint 14 (indicated in FIG. 4 both on the platform and the A-frame) withplatform 12 to a pair of pivoted connections 26 and 28 with transfertruss 30. A-frame 20 and truss 30 form a mechanical linkage throughwhich pitch motion is transmitted to platform 12, Truss 30 is pivotallyconnected at points 32 and 34 to vertical translation truss 36, and isfurther pivotally attached at point 38 to the end of the piston rod ofpitch cylinder 40, the other end of which is pivotally attached at 41 toa support on truss 36. Roll cylinder 24 is likewise pivotally supportedat point 42 upon vertical translation truss 36.

A-frame 22 extends from its connection at point 18 (also indicated onboth the platform and the A-frame) with platform 12 to a pair of pivotalconnections 44 and 46 upon horizontal member 48 of vertical translationtruss 36. Extensible cylinder 50 is attached at one end to A- frame 22at point 52 and at the other end at point 54 to horizontal member 56 ofvertical translation truss 36. Although roll cylinder 24 and pitchcylinder are programmed, servoed actuators which produce controlledmotion of platform 12 about axes XX and Y--Y, respectively, extensiblecylinder is used merely for moving the support point 18 between twopositions, as will be more fully explained hereinafter. In one suchposition (FIG. 1) platform 12 is in a rest position with the power toall actuators turned off, and in the other (FIG. 2) the platform is inan operative position for movement under control of the actuators. Thus,there is no necessity for any control of the rate of movement ofcylinder 50 which, in the proper sense, is not a motion actuator.

The mechanism by which vertical translation is imparted to platform 12is shown in greater detail in FIG. 5. Vertical translation truss 36 ispivotally connected adjacent each of its four corners indicated byreference numbers 58, 59, and 61, to respective points 62, 63, 64 and oneach of four rigid, triangular bell crank members 66, 68, and 72,respectively. While the bell cranks may be attached to fixed mountingsat two of the corners (e.g., 58 and 59) of truss 36, mountings allowingsome movement to compensate for slight fore-and-aft misalignment shouldbe used at the other two corners (e.g., the shackle mountings shown at60 and 61). The two forward bell cranks 66 and 68 are rigidly connectedby torsion tube 74 and the two rear bell cranks 70 and 72 are connectedby torsion tube 76. The torsion tubes are rigidly connected, e.g., bywelding, to each of the bell cranks which they connect, wherebyrotational movement of the bell cranks on either side is transmittedprecisely to the corresponding bell crank on the opposite side. Also,the forward and rear bell cranks 66 and 70 one side of the apparatus aretied together by tension rod 78 which is pivotally attached at itsopposite ends to portions of the bell cranks. Likewise, bell cranks 68and 72 on the opposite side of the apparatus are tied together bytension rod 80 in the same manner. Truss structures 81 and 83 providelateral rigidity between the front and rear pairs of bell cranks,respectively. The four bell cranks are pivotally mounted upon fixedsupports 82, 84, 86 and 88 by means of fixed brackets 90 and 92 ontorsion tube 74 and fixed brackets 94 and 96 on torsion tube 76. Forwardfixed supports 82 and 84 are connected by rigid truss structure 98, andrear fixed supports 86 and 88 are connected by truss structure 100. Thefixed supports may be attached to the fioor to other suit able basesupport structure such as longitudinally extending I-beams 102 and 104,and laterally extending I-beams 106 and 108. Vertical translationcylinders 110 and 111 have their movable ends pivotally secured at 112and 113 to bell cranks 66 and 68, respectively, and are pivotallyattached at the other ends 114 and 115 to fixed mountings 116 and 117 onI-beam 106. It will be noted that although torsion tubes 74 and 76enhance the structural rigidity they do not add to the weight which mustbe lifted in order to elevate platform 12 since they move downwardly asthe platform is elevated.

The structure thus far disclosed is suitable for providing motion inthree degrees of freedom to platform 12, and therefore to studentstation 10. As shown in FIG. 1, platform 12 is in the rest or settledposition with cylinders 24, 40 and 110 in their fully retractedpositions. Likewise, erecting cylinder 50 is in its fully retractedposition and platform 12, due to the geometric relationships of thecylinders and other structural elements, is in a level position whereinpower to the actuators may be turned off. Simultaneous extension oferecting cylinder 50, and pitch and roll cylinders 40 and 24 will moveplatform 12 to the position shown in FIGS. 2 and 3. In this position,erecting cylinder 50 is fully extended, but the pitch and roll cylindersare extended only to such an extent that they are capable of producingmotion of platform 12 to the desired extent in both directions abouteach of axes XX and Y-Y. In moving from the settled to the erectedposition, extension of cylinder 50 is transmitted through A- frame 22 toelevate support point 18 of platform 12, while extension of pitchcylinder 40 is transmitted through truss 30 and A-frame 20 to elevatesupport point 14, and extension of roll cylinder 24 directly elevatessupport point 16.

Before commencing any controlled motion program for cockpit 10 verticaltranslation cylinders 110 and 111 would be extended from their fullyretracted positions to an intermediate position from which bothelevation and descent of platform 12 along the vertical axis could beachieved. As may be readily seen from the drawings, equal extension ofcylinders 110 and 111 revolves all of bell cranks 66, 68, 70 and 72 anequal extent about their respective pivotal mountings in acounterclockwise direction as seen in FIGS. 1 and 2. Such rotation willdirectly elevate vertical translation truss 36, and thereby platform 12and cockpit 10. Descent of the platform may be achieved by counterrotation of the bell cranks as cylinders 110 and 111 are retracted. Thepivotal mounting of fixed ends 114 and 115 of cylinders 110 and 111allows arcuate movement of the other ends about the pivotal mountings ofthe bell cranks on fixed mounts 82 and 84. Since the bell crank memberswhich transmit movement of cylinders 110 and 111 to truss 36 are tiedtogether to form a structurally closed-loop system, there is essentiallyno uneven backlash or lost motion in the vertical translation systemfrom side to side or front to rear. Any unevenness in motion ofcylinders 110 and 111, for example, due to leakage of fiuid past acylinder, will be compensated for by torsion tubes 74 and 76. Thislinkage also simplifies ganging of vertical translation actuators, suchas cylinders 110 and 111 (and others, if desired), as well as theaddition of balance cylinders connected to bell crank 70 and/or 72.Likewise, pitch and roll cylinders may be ganged, or balance cylindersadded. Since ganged cylinders may be actuated with the same servo valve,the problems associated with synergistic actuators do not arise. It willbe noted that although vertical motion of platform 12 may be implementedthrough simultaneous extension or retraction of erecting cylinder 50 andpitch and roll cylinders 40 and 24, such motion would require synergismof these three actuators, which is a feature specifically avoided by thepresent motion system.

It will also be readily apparent to those skilled in the art that motionin the other three axes of freedom, in addition to the three disclosed,may easily be added to the system. For example, translational motionalong the X and Y axes of the entire apparatus, and thereby of cockpit10, could be achieved by mounting the l-beams of the base section uponsuitable rollers, air bearings, or the like. Rotation about a verticalaxis through point 18 (i.e., yaw motion) may be achieved by mounting thesupport for the ball joint of A-frame 20 in a slider block laterallymovable with respect to the remainder of platform 12 and mounting anactuating cylinder between the slider block and one side of theplatform. A limited amount of fore-and-aft horizontal translation,sufficient for most purposes, may be achieved in a like manner bymounting the support for the ball joint of A-frame 22 in a slider blockmovable along the X axis and adding an actuator to effect such movement.Although support point 14 will move in a slight arc during suchfore-and-aft motion, the ball joint of A-frame 20 would be near the topof the are at all times with the illustrated geometry and any pitchmotion would be imperceptible.

What is claimed is:

1. A motion simulator capable of providing controlled motion in any ofseveral degrees of freedom to the student station of a vehicle trainer,or the like, said simulator comprising, in combination:

(a) a first rigid support frame to which the student station is afiixedfor common movement;

(b) a second rigid support frame to which said first frame is pivotallyconnected for movement in at least one rotational degree of freedom;

(c) an immovable base relative to which said second frame is movable inat least one translational degree of freedom;

(d) a first pair of bell crank members mounted for rotation about acommon, fixed axis and each pivotally connected between said secondframe and said base at one end and on opposite sides thereof;

(e) a second pair of bell crank members mounted for rotation about acommon, fixed axis and each pivotally connected between said secondframe and said base on opposite sides and at the end thereof oppositesaid first pair;

(f) first means extending laterally between said first pair of bellcrank members and rigidly attached to each, whereby rotation of one ofsaid first pair is transmitted to the other through said first means;(g) second means extending laterally between said second pair of bellcrank members and rigidly attached to each, whereby rotation of one ofsaid second pair is transmitted to the other through said second means;(h) first reciprocally movable motion actuator means connected betweensaid first and second frames for imparting motion to said first framerelative to said second frame in said rotational degree of freedom;

and

(i) second reciprocally movable motion actuator means connected to oneof said pairs of bell crank members to impart common rotational movementthereto,

15 thereby imparting movement to said first and second frames relativeto said base in said translational degree of freedom.

2. The invention according to claim 1 wherein said first and secondmeans comprise torsion tubes welded to each of the respective bellcranks of said first and second pairs.

3. The invention according to claim 1 and further including third meansextending between and pivotally connected to each of the bell crankmembers of opposite pairs on each side of said motion frame and base.

4. The invention according to claim 3 wherein said third means comprisetension rods through which rotation of any one of said bell crankmembers is transmitted directly to the bell crank members of the otherpair.

ROBERT W. MITCHELL, Primary Examiner L. R. OREMLUND, Assistant Examiner

